Did your letter include a specific accusation of your boss of bullying you?

No I said “I feel like you have bullied me because of your own bad mood”

What country are you in? And generally speaking anyone can sue anyone for anything, now whether they will be successful is a whole other story.

The UK, and yes I guess so

Did you publish your notice letter anywhere public? You can't exactly hurt your bosses' reputation if he's the only one that knows what it says.

No, it went to him and only him

So long as you don't intend to publicly accuse your boss of bullying you do not need a solicitor. In the incredibly unlikely event that your boss or your employer tries to sue you, only then should you get one. You could contact ACAS in the UK who purport to give free advice on workplace problems, including legal ones. I am not in the UK and don't know that organisation's reputation so you should probably do some research or ask some friends what they think of them first.

Okay, thank you Eric

Interesting, though, that his indignant response to your accusation of him bullying you, is to attempt to bully you!

He also dismissed my mental health and said “he’s not having that” as an excuse for my resignation either

You can get sued for just about anything. Given your description though, it is doubtful they will sue you, and even less likely for them to win.

@EricNolan, ACAS is a Quango - a (relatively) independent arm of the government. They are super legit and are recognised in many contracts as the arbiter of any disputes. Definitely contact them or the Citizens’ Advice Bureau (an independent charity).

@Gordon. "Boss, I have resigned. I have given the statutory amount of notice, so you have x weeks to find my replacement and bring him up to speed. I will, or course, provide as much assistance as I am required to by my contract. It is entirely your choice whether you spend this time constructively or not. If you choose not to, I trust that you can live with the consequences".

Slander is spoken defamation; libel is written defamation; and in either case it needs to be published to be actionable. So clearly he has not consulted a solicitor himself; and when he does, if he does, he will discover all this for himself. Forget about it.